OIP Type Voltage Transformer

12kV - 145kV post type voltage transformers having Oil Impregnated Paper( OIP) as major insulation has been designed with several unique features.

OIP insulated outdoor products are subjected to extreme climatic conditions and hence extra care is taken in the design and manufacturing of such transformers.

The major design care of these products is therefore aimed at the following five areas:

Reliability, Hermetic Sealing, Maintenance, Handling / Installation & Safety


  • True Hermetic Sealing: Ensure that each unit is truly hermetically sealed so that it retain the insulation properties for many years of service life.
  • Reliability: Reliability is ensured at every design aspects and each process the product undergoes. Our entire range of products are highly standardised in its engineering design which is one of the key elements in ensuring high reliability.
  • Maintenance: Our products are truly maintenance free. Only periodical cleaning of insulators are required to be done.
  • Handling / Installation: We also give equal importance to the user-friendliness right from unpacking to the erection.
  • Safety: Even in the event of an unfortunate failure of the product, safety comes first. In the event of an internal failure the bellow acts as pressure relief device which peels off from the tank and thereby avoid any explosions.


Design Highlights

Low Eddy Current Heating even at higher currents.

Resilience effect - Absorbs mechanical shocks on primary terminals.

Lumped Primary Winding with rectangular copper strips - Provides high strength during STC.

Specially designed rectangular copper lugs for primary winding termination - Give strong and reliable joints.

Capacitively graded Insulation - Aids uniform voltage distribution and partial discharge free performance.

Crimped joints on secondary leads.

Cemented flanges on insulator - uniform stress distribution.

True hermetic sealing - life long factory fresh insulation properties.

Process Highlights

Main insulation is dried as by proven procedures under controlled vacuum and temperature.

The EHV grade transformer oil is degassed and filtered until the desired properties are met (BDV > 75 kV).

Each unit is pneumatically pressure tested at lkg/cm2 at various assembly stages in order to ensure effectiveness of sealing points.

Oil is filled from the bottom under controlled vacuum and temperature and at an established steady & slow rate.

After oil flooding, each unit is hydraulically pressurized at lkg/cm2 for 6 hours to check effectiveness of sealing.

Extreme care is taken to assure adherence to the paint finishing process ensuring adequate time gap between each coat.